In systems where digital data is encoded by an encoder, transmitted in packets of digital data, and decoded by a receiver, the encoder may receive data that includes digital samples of analog signals. The encoder groups the samples into packets for transmission to a decoder. The encoder places time stamp data in the packets. The time stamp data represents the value of the encoder clock at various intervals, so that the decoding and encoding can be synchronized. In hardware decoders (for example, set-top boxes) the clock values represented in the time stamps are used to synchronize the decoder clock with the clock used to encode the data. Different time stamps may be used, for example, to indicate presentation time (the time at which a packet should be rendered (played), decode time (the time at which a packet should be decoded), and the reference value of the encoder system clock (at the time the data packet is created)). These time stamps are known as presentation time stamps (PTS), decoding time stamps (DTS), and system clock references (SCR).
When there is a break or discontinuity in the series of PTS, media playback may suffer. For example, an initial (i.e., starting) video frame may begin with a non-zero PTS while the audio frame begins with a 0 PTS. Such a situation can occur, for example, when a video stream is cut from another video stream and the initial position of the cut stream does not coincide with a key-frame (e.g., I frame). Consequently, in streams containing video and audio, one can hear audio but the picture is static (e.g., a blank screen) until playback time reaches the PTS of the first video frame. During presentation of the static picture, audio may continue thereby frustrating the viewer. Skipping the audio data that precedes the first video PTS is also frustrating to the viewer.